INTERACTION BETWEEN LEAKAGE FLOWS AND PASSAGE FLOWS IN TURBINES

Turbine is a part of gas turbine engine which extracts energy from working fluid. Efficiency of turbine is an useful indicator to evaluate performance of turbine since it determines operating cost per power. In modern gas turbines turbine inlet temperature is as high as 1800K for better efficiency. The ingestion of hot gas through the unavoidable gaps between rotating and stationary parts damages turbine discs. To prevent such damage, compressor air is fed into the rotor-stator wheelspace, and this flow is referred to as the purge flow.
In previous researches, purge flow from hub with low momentum strengthens hub passage vortex and thus increases total pressure loss. With increasing mass flow rate of purge flow total pressure loss increases  but increasing tangential velocity in rotating direction has opposite effect. Where as most of previous researches the interaction berween purge and main annulus flow has been investigeated at the hub side, this research aims to investigate the interaction between purge from casing and tip clearnce flow. Furthermore, correlation between pruge flow properties (e.g. mass flow rate, swirl ratio and pitch angle) and total pressure loss. Low speed linear turbine cascade will be conducted for this purpose of research.